The invention relates to a method of and device for monitoring combustion in an internal combustion engine operable with spark ignition.
If, in an internal combustion engine operable with separate ignition, the introduced fuel is not burnt in the engine combustion chambers, such unburnt fuel becomes purged into the exhaust system. The high temperature prevailing in the exhaust system can cause such fuel to be ignited there, and in particular in an exhausts gas catalyser, which can lead to destruction of the exhaust system.
It has been proposed to monitor the combustion of the fuel/air mixture by measuring the combustion pressure in an engine cylinder. This is not very practical except for research purposes. It has also been proposed to measure ionisation current at the spark plugs. This needs sophisticated equipment.